Is Dual channel programmer on combi boiler wrong?

Beckyy

Will try and keep it simple:

Oil fired combi boiler, used to have a very old dual channel controller on when we first moved in, we just ignored the water part as was on demand. House was empty for a while and this needed replacing. OH bought the new equivalent (Drayton lifestyle LP241) and wired it the same as previous one (is a qualified electrician).

The boiler was then heating hot water to the right temperature constantly rather than only when the tap was on, using oil unecessarily. When the boiler was serviced engineer said it was wired wrong as hot water was set to be on constanty so changed it. Now the hot water won't work on demand... it has to be put 'ON' at the programmer for water to be heated, and in turn is on constantly keeping the water at the temperature ready to go straight out, but wasting oil doing this.

As it's a combi boiler should it actually have a Single Channel Programmer like this?:

http://www.draytoncontrols.co.uk/LPTimeswitchRange.aspx



We have a new tenant moving in at the end of the week so as I have to order one in I need to make sure it's the right one! Thanks for any help.

gas4you

If it is a genuine combi, then you only need a single channel programmer for the heating side.

Some newer combi's have a timer for the DHW pre-heat times, but the DHW remains on demand.

Beckyy

Thanks gas4you, it's a genuine combi about 5 years old so not super new. We bought one the same as pictured from B&Q and OH wired as before and it's spot on now! Thanks.

mark-w20

Combi should have programmer for heating and hot water, it's in the building regs as "time and tempi true control for heating and hot water" without timer boiler will permanently keep its store at stanby temp possibly firing burner during night etc. your engineer was right.

southcoastrgi

mark-w20 wrote: »

Combi should have programmer for heating and hot water, it's in the building regs as "time and tempi true control for heating and hot water" without timer boiler will permanently keep its store at stanby temp possibly firing burner during night etc. your engineer was right.

complete rubbish,

OP just set the timer on the H/W to on rather than once or timed

Silent_Dancer

As its an oil combi it is likely to have an inbuilt thermal store and this should be on a timer to save energy. The burner will fire to bring the thermal store up to temperature and then you can produce hot water.

mark-w20

southcoastrgi wrote: »

complete rubbish,

OP just set the timer on the H/W to on rather than once or timed

So you want the burner firing up when no hot water is required ie overnight, programmer prevents that meaning burner can only fire when occupants have set timer to on. What's the point in the boiler being allowed to fire it's burner to maintain store temp at 3 am for instance.
I'll stick with my original answer twin channel programmer is best.

gas4you

A standard combi, which the OP says she has, only fires up on demand for hot water, ie when the hot tap is turned on and does not have a storage tank.

Some may fire occasionally to operate the preheat only, but this cannot be timed usually.

mark-w20

An oil combi has a thermal store of primary water which it keeps at a standby temp in order to make hot water through a plate exchanger, so whereas it does not store "hot water" it does store hot primary water which is why a programmer is better on hot water as well as heating else it will fire the burner at intervals when possibly no hot water demand is likely, ie at night and during working hours when the property is possibly empty.

matelodave

Would it not be better to know exactly which boiler the OP has before deciding what he needs.

Most combi's dont need a timer on the hot water circuit because they just heat water on demand - although I'd agree that if its got a thermal store/pre heat function then it might.

But you can't give definitive advice unless you know whatt he's got

Beckyy

It's a ' worcester greenstar heatslave 18/25'. I haven't had any problems with it firing up when the tap isn't on since the single channel control was fitted. Turn the tap on and it fires up, tap off and it stops. Nothing inbetween that I've noticed and I was there for some time the last few days.